1. Technical Field
The present invention relates to a disk drive apparatus such as a hard disk drive, and relates in particular to a head assembly for performing reading and writing of data on a recording disk, and a head assembly pivot bearing.
2. Description of the Related Art
Disk drive apparatuses such as a hard disk drives are widely used as the main storage destination for data in computer apparatuses. This kind of disk drive apparatus is configured by a recording disk or disks for recording data, accommodated in a housing called a disk enclosure. One or a plurality of recording disks are attached in freely rotatable fashion to a spindle fixed to the housing, and are rotated by a spindle motor. Close to the recording disks is located a head assembly for performing reading and writing of data on the recording disks.
The head assembly is attached so as to be free to pivot to a pivot shaft fixed to the housing of the disk drive apparatus. This head assembly is equipped with an arm that extends on one side with respect to the pivot shaft, and a magnetic head is attached to the end of this arm. A coil support is attached to the opposite side of the arm, enclosing the pivot shaft, and a coil which is a component of a voice coil motor (VCM) for driving this head assembly is held by this coil support.
Located opposite the head assembly coil is a stator which is a component of the VCM, and the head assembly is driven about the pivot shaft by varying the magnetic field generated between the stator and the VCM. As a result, the magnetic head attached to the end of the head assembly arm moves along the surface of a recording disk, and reading of data recorded on a recording disk or writing of data to a recording disk is performed by accessing the target track on the surface of a recording disk.
Now, the storage capacity of disk drive apparatuses has grown remarkably in recent years, and in line with this, the recording density of data on the recording disks has increased. Consequently, the distance between tracks in the radial direction of the recording disks has become smaller, and the trend is one of demand for higher precision for positioning on the tracks on which target data is stored when reading data with a magnetic head.
Also, with the increase in storage capacity, there is a demand for faster reading and writing of data on the recording disks. While it is all very well to perform high-speed processing of data that is read or written with a magnetic head, improving the speed of the mechanical rotation of the head assembly when the magnetic head accesses (seeks) the target track on a recording disk is a major problem.
In speeding up the operation of the head assembly in this way, and moreover improving the precision of magnetic head positioning, the mechanical precision of the head assembly, and more specifically, the location of the center of gravity when the head assembly pivots about the pivot shaft, has a major influence. That is to say, a shift in the location of the center of gravity of the head assembly has greater influence the more the rotational operation of the head assembly is improved. As a result, the positioning precision with respect to the target track decreases, and this may lead to the occurrence of data read/write errors.
For this reason, adjustment of the location of the center of gravity of the head assembly has been carried out heretofore in the design stage or prototype production stage. This involves adjusting the shape of a resin member, etc., that supports a flexible plate provided to transfer signals that are read or written by means of the coil support, arm, and magnetic head comprising the head assembly. More specifically, a depression, etc., is formed in the coil support, arm, resin member, etc., and adjustment is performed so that the location of the center of gravity during pivoting of the head assembly is close to the axis of the pivot shaft.
3. Problems to be Solved by the Invention
However, this kind of head assembly is configured by a plurality of members such as a coil support, arm, VCM coil, magnetic head, and pivot shaft, bearing. Therefore, even if each member is manufactured within predetermined manufacturing tolerances, when these members are assembled to form the head assembly, the accumulation of error within the manufacturing tolerance ranges of the individual members may result in a displacement of the location of the center of gravity of the head assembly.
Also, when forming a depression in the coil support, arm, resin member, etc., comprising the head assembly, for productivity reasons these members are stamped or molded. Consequently, when adding a depression for balance adjustment, or changing its dimensions, modifications must be made to the dies used for forming. Die modifications require a great amount of cost and time, and this also hinders improvement of the product development speed.
Further, since such members, and particularly the coil support, arm, etc., are stamped, it is not possible to control the dimension in the direction of the thickness of the material. Consequently, even if adjustment of the location of the center of gravity of the head assembly is attempted by forming a depression, etc., in these members, it is only possible to adjust the error in the location of the center of gravity by some tens of μm. Of course, in the prototype production stage, the location of the center of gravity of the head assembly can be adjusted to a higher degree of precision by repeating die modifications while observing these results, but it goes without saying that this involves great increases in cost and time.
The present invention takes account of such technical problems, and its object is to provide a disk drive apparatus, head assembly, and so forth, that enable balance of the head assembly to be achieved with high precision, in an efficient and sure manner.